Two prisoners died on Friday and Saturday while a third died Monday after admission to a hospital in Sri Lanka.
The incident has resulted in the sacking of the police chief by President Aumoon Abd al-Gayoom, and the arrest of six more National Security Service (NSS) men, raising to 11 the total number of security personnel in detention over the killing of inmates at the Maafushi prison.
Riots reportedly broke out after police tried to cover up the murder of an inmate by policemen at the prison.
News of the inmate’s murder and secretive burial triggered unrest in the prison and protests in the capital city of Malé.
Protests turned into riots however as mobs torched the elections office, the high court, several police stations and police vehicles and stoned other public buildings, including the nation's main international conference centre.
"It is high time that government authorities accept their own responsibility and failure to protect and promote human rights"
The latest death coincided with President al-Gayoom winning all 50 votes in parliament.
He has secured a sixth five-year term to lead the tiny nation of 1192 coral islands, the most expensive tourist destination in the Indian Ocean.
At least 12 inmates have been flown to neighbouring Sri Lanka with serious gunshot wounds.
Maldivian authorities have stressed the unrest was unrelated to the re-election bid of al-Gayoom.
But human rights’ group Amnesty International linked this week’s rioting to violations of human rights and the abuse of power by security officials.
"By repeatedly dismissing reports of human rights violations in the country, the Government of President Gayoom has allowed perpetrators to continue to act with impunity."
"It is high time that government authorities accept their own responsibility and failure to protect and promote human rights," Amnesty International said in a statement.